====== Ontology Introduction ======
  * http://ontologydesignpatterns.org/wiki/Training:Tutorial:_Methods_and_Tools_for_Modular_Ontology_Modeling
  * https://stackoverflow.com/questions/51615618/owl-proteg%C3%A9-using-the-same-object-property-for-different-domains-ranges
    * https://henrietteharmse.com/2018/05/10/understanding-owl-universal-property-restrictions/
  * 
===== Headline =====